Ab initio molecular dynamics investigation of the formyl cation in the superacid SbF5/HF

The formyl cation (HCO⁺) is an intermediate involved in electrophilic formylation reactions of aromatic compounds. We have employed ab initio molecular dynamics simulation to investigate free energy profiles along several possible reaction paths for CO in the SbF₅/HF superacid solution for different concentrations of SbF₅. The formation of the HCO⁺ cation is optimally favored in the 1:1 SbF₅/HF solution. However, no evidence has been found for the presence of either the isoformyl cation, COH⁺, or the protoformyl dication, HCOH²⁺. A novel mechanism for the experimentally observed fast proton exchange in the system CO in 1:1 SbF₅/HF is proposed.